title: Functional interaction of the circadian clock and UV RESISTANCE LOCUS 8-controlled UV-B signaling pathways in Arabidopsis thaliana.
abstract: Circadian clocks regulate many molecular and physiological processes in Arabidopsis (Arabidopsis thaliana), allowing the timing of these processes to occur at the most appropriate time of the day in a 24-h period. The accuracy of timing relies on the synchrony of the clock and the environmental day/night cycle. Visible light is the most potent signal for such synchronization, but light-induced responses are also rhythmically attenuated (gated) by the clock. Here, we report a similar mutual interaction of the circadian clock and non-damaging photomorphogenic UV-B light. We show that low-intensity UV-B radiation acts as entraining signal for the clock. UV RESISTANCE LOCUS 8 (UVR8) and CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) are required, but ELONGATED HYPOCOTYL 5 (HY5) and HY5 HOMOLOG (HYH) are dispensable for this process. UV-B responsiveness of clock gene expression suggests that photomorphogenic UV-B entrains the plant clock through transcriptional activation. We also demonstrate that UV-B induction of gene expression under these conditions is gated by the clock in a HY5/HYH-independent manner. The arrhythmic early flowering 3-4 mutant showed non-gated, high-level gene induction by UV-B, yet displayed no increased tolerance to UV-B stress. Thus, the temporal restriction of UV-B responsiveness by the circadian clock can be considered as saving resources during acclimation without losing fitness.
authors.affiliation: Institute of Plant Biology, Biological Research Centre of the Hungarian Academy of Sciences, H-6726 Szeged, Hungary.
authors.forename: Balázs
authors.initials: B
authors.lastname: Fehér
authors.forename: László
authors.initials: L
authors.lastname: Kozma-Bognár
authors.forename: Eva
authors.initials: E
authors.lastname: Kevei
authors.forename: Anita
authors.initials: A
authors.lastname: Hajdu
authors.forename: Melanie
authors.initials: M
authors.lastname: Binkert
authors.forename: Seth Jon
authors.initials: SJ
authors.lastname: Davis
authors.forename: Eberhard
authors.initials: E
authors.lastname: Schäfer
authors.forename: Roman
authors.initials: R
authors.lastname: Ulm
authors.forename: Ferenc
authors.initials: F
authors.lastname: Nagy
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D050976:Basic-Leucine Zipper Transcription Factors / Q000502:physiology; D002352:Carrier Proteins / Q000502:physiology; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism*; D057906:Circadian Clocks / Q000502:physiology* / Q000528:radiation effects; D002940:Circadian Rhythm / Q000502:physiology / Q000528:radiation effects; D004268:DNA-Binding Proteins; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D009154:Mutation; D009687:Nuclear Proteins / Q000502:physiology; D017440:Photoperiod; D015398:Signal Transduction / Q000502:physiology*; D013312:Stress, Physiological; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D044767:Ubiquitin-Protein Ligases; D014466:Ultraviolet Rays
chemical_list: D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; D002352:Carrier Proteins; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors; D044767:Ubiquitin-Protein Ligases; C114425:CCA1 protein, Arabidopsis; C432430:At2g25930 protein, Arabidopsis; C465973:ELF4 protein, Arabidopsis; C109254:HY5 protein, Arabidopsis; C457459:HYH protein, Arabidopsis; C525052:Uvr8 protein, Arabidopsis; C471983:AT2G32950 protein, Arabidopsis